In recent years, streetcars and the like have adopted low floor vehicle designs in which a floor surface in the vehicle is set close to a road surface to reduce the difference in level for stepping up and down for passengers so as to make the vehicles barrier-free. In such a streetcar, because of limitations such as road traffic conditions, a large number of curved tracks curving with a curvature radius equal to or less than 20 m are provided. A low floor vehicle having a low center of gravity because of the structure thereof can travel relatively stably on such curved tracks. However, there is a problem in that, when the vehicle enters a curved track, an angle in a traveling direction of wheels with respect to a tangential direction of the curved track (hereinafter referred to as “attack angle”) increases. When this attack angle is large, in wheels present on an outside rail during travel on the curved track, in some cases, flanges of the wheels come into contact with the track. At this point, pressure is applied from the wheel flanges to the vehicle, the lateral pressure of the vehicle increases, and vibration and creaking sounds occur in the vehicle. As a result, there is a problem in that riding comfort for passengers is degraded and the wheel flanges wear out.
Taking such a problem into account, a low floor vehicle called an LRV (Light Rail Vehicle) as disclosed in Patent Document 1 has been developed. In FIG. 7, an example of the configuration of this LRV is shown. A traveling direction of this LRV is indicated by an arrow A. In the explanation, it is assumed that the traveling direction is to the vehicle front. Referring to FIG. 7, the LRV includes two front vehicles 102 and one intermediate vehicle 103 traveling on a track 101. As a vehicle composition, the one intermediate vehicle 103 is arranged between the two front vehicles 102.
Pin connectors 105 are arranged along an axis extending in a vehicle vertical direction in connecting sections 104 between the front vehicles 102 and the intermediate vehicle 103. The front vehicles 102 are coupled to the intermediate vehicle 103 to be capable of turning around the pin connectors 105. Therefore, the front vehicles 102 and the intermediate vehicle 103 can curve around the pin connectors 105 to correspond to a curvature radius R of the curved track 101. Furthermore, in the connecting sections 104, dampers, springs, or the like (not shown) are provided to suppress the turning of the front vehicles 102 and secure safety during high-speed travel of the vehicle.
Bogies 107 are arranged under vehicle bodies 106 of the front vehicles 102. As shown in FIGS. 8 to 10, a pair of wheels 108 is provided at each of a vehicle front direction and a vehicle rear direction of the bogie 107. The pair of wheels 108 are configured to be pivotable independently of each other around the same axis 108a extending in a vehicle lateral direction and coupled by a journal member 109. The journal member 109 is arranged at each of a vehicle front direction and a vehicle rear direction of each of bogie frames 110 formed as frame members of the bogie 107. Conical rubber 111 is provided as a shaft spring for the wheel 108 between the journal member 109 and the bogie frame 110. Vibration transmitted from the wheel 108 to the bogie frame 110 is suppressed by this conical rubber 111. Furthermore, the journal member 109 extends at a position close to the road surface between the pair of wheels 108. A floor surface (not shown) in the vehicle is arranged at the journal member 109. Therefore, the floor surface in the vehicle is configured to be close to the road surface.
Referring to FIG. 7 again, when the vehicle traveling in the traveling direction enters the curved track 101, force directed in a straight forward direction by inertia acts on the vehicle bodies 106. Force directed in a curving direction along the curved track 101 acts on the bogies 107. Therefore, force acting on the entire front vehicles 102 is unbalanced. At this point, the straight forward force by inertia also affects the bogies 107. The bogies 107 are less easily curved along the curved track 101. As a result, an attack angle α, which is an angle in the traveling direction (indicated by an arrow C) of the wheel 108 with respect to the tangential direction (indicated by an arrow B) of the curved track, increases. It is likely that wheel flanges 108b (shown in FIGS. 8 to 10) of the wheels 108 on an outside rail side come into contact with the track. At the time of this contact, pressure is applied from the wheel flanges 108b to the vehicle, lateral pressure of the vehicle increases, and vibration and creaking sounds occur in the vehicle. As a result, there is a problem in that riding comfort of passengers is degraded and the wheel flanges 108b wear out.
To absorb such unbalance of force, the bogies 107 are configured to be movable in the vehicle lateral direction with respect to the vehicle bodies 106. Specifically, as shown in FIGS. 8 to 10, traction rods 112 that transmit traction force of the bogie 107 to the vehicle body 106 are arranged along a vehicle longitudinal direction. Ends 112a on the vehicle rear direction of the traction rods 112 are attached to the bogie 107 side via a spherical bush or a rubber vibration insulator (not shown). Ends 112b on the vehicle front direction of the traction rods 112 are attached to the vehicle body 106 side via a spherical bush or a rubber vibration insulator (not shown).